Strontium titanate, SrTiO3, has been measured at high frequencies in wide temperature range by Prof. Petzelt (Institute of Physics, Prague, Czech Republic) and co-workers.

Pls check firstly the following articles:

1. http://pubs.acs.org/doi/abs/10.1021/cm803058q

2. http://www.tandfonline.com/doi/abs/10.1080/10584580490457820#.VA275SjeeLo

I hope it will help you in your work.

I found both articles at ARXIV,

 have a plot where the permittivity begin to fall from 100Hz, but in both articles it falls at gigahertz range, perhaps the problem is with the reflectance test of the dielectrics. Does the reflectance system gives the same result than using electronics system?

Note: the second article is related to another ceramics.

Our experience is less than in other titanates(  Ba or Ca). However, I know that the group from Institute of Physics from Prague and Faculty of Physics, Vilnius University , Lithuania measured many titanate based materials in a wide frequencies interval . You can contact them ( group of  Prof. Juras Banys)

Dear B.D.,

Does the institute uses electric measurement, reflectance method or other?

Strontium titanate works very good at frequencies up to 10 GHz and may be higher (we have not test that) in thin film forms. STO can be applied as high quality substrate for other films (e.g. YBCO superconductors) or as non-linear dielectric. The films has relatively low dielectric losses but keep tunable permittivity. You can see results for tunable capacitors in the works of Prof. Kozyrev group from Saint-Petersburg Electrotechnical University.

Article Ferroelectric film phase shifter under elevated microwave power

Article Switching time of planar ferroelectric capacitors using stro...

Article Ferroelectric Strontium Titanate Thin Films for Microwave Applications

Article Ferroelectric Tuning of Planar and Bulk Microwave Devices

Article Nonlinear Behavior of Thin Film SrTiO3 Capacitors at Microwa...

Article Permittivity of strontium titanate film in a SrTiO 3 /Al 2 O...

Article Nonlinear properties of SrTiO3 films at microwave frequencies

It is a pity that the documents are not available in  research gate.

I have seen in other paper a ceramics have a relative permittivity over 1200 at 100Hz, but came lower at higher frequencies. There are other ceramics (with different thermal treatment) with lower permittivity that works to gigahertz. It may be difficult to have both.

Another problem to build high capacitance for high frequency is the dielectric breakdown. I have seen articles where the ceramics powder is mixed with a plastic binder giving some increase of the voltage but at the cost of a loss in the permittivity.

It would be wonderful if somebody made a capacitor using graphene or high temperature superconductor as Alexander said, with separate layers of high strength dielectrics sandwich with SrTixx E>1200 ceramics.

About the papers posted by Alexander, I have seen that used ceramics does not contains barium. Works better the ceramics at high frequency without barium?

Pay attention that SrTiO3 that was successfully used at microwave was polycrystalline film with submicrone thickness (not ceramics). We estimate the permittivity of this film in only about 1000.

The temperature peak of permittivity was observed rather flat and permittivity does not change significantly (no more than two times) from peak value at about 70K  (in spite of virtual ferroelectricity of bulk material) to room temperature value.

Application of  "clean" SrTiO3 rather than solid solution BaxSr1-xTiO3 certainly leads to the decreasing of permittivity of films but tunability K keep its value at K>2 at dielectric losses no more than tan_delta = 0.01.

I can try to find and send you full-texts of papers mentioned.

I am impressed by the high frequency properties of the SrTiO3.

You named it as a polycrystalline film, what is the substrate?

It is ferroelectric, so perhaps it has a high relative permeability could speed down the capacitors, as long as the discharge time is sqrt(L/C) where L is the inductance that is proportional to permeability.

Thank you for uploading the document (I voted them), good for open science

The SrTiO3 should response about GHz, as sended above see papers Prof Petzelt. The ferrolectric response is another question.

Ferroelectric response (with spontaneous polarization, hysteresys loop and coercive voltage) is another question, of course. Actually SrTiO3 is virtual ferroelectric and in bulk form have no ferroelectric response.  But in thin film form temperature peak of permittivity can be observed at about 50K (without bias voltage).

I hope we are talking about non-linear dielectric response of STO.

In our works we use SrTiO3 films grown by ion-plazma techology on Al2O3 substrate (both polycrystalline alumina and monocrystalline R-cut sapphire) with or without bottom Pt conductive layer (for planar or sandwich capacitors). The films are textured with single-crystal blocks with sizes of (20. . . 40) nm and (100), (111), and (110) orientations normal to the substrate surface.

As for permeability... we have metal electrodes which have inductive response that exceeds any permeability effect in dielectric. But resonant frequency is about 30GHz for capacitors designed for 1GHz working frequency, so self-resonance can be neglected.